This invention relates to a food product and more particularly to a semi-moist food product containing color stabilized animal protein which food product is suitable for either human or pet consumption.
Within the class of pet foods, there are three general subdivisions -- dry pet food, moist pet food, and semi-moist pet food. Stability after the pet food package is opened is critical. Dry pet food tends to be the most stable pet food with the least sophisticated packaging required to maintain that stability. Customarily, dry pet food is not as palatable as the other types of pet food. Semi-moist pet food tends to be a relatively stable pet food requiring somewhat more stringent packaging conditions than dry pet food, but with a corresponding increase in palatability. Moist pet food tends to be the most palatable of the three classes of pet food, but requires the most stringent packaging conditions. However, moist pet food is still the most acceptable to pet owners and pets.
It is generally accepted that any member of the class of pet foods must please the owner of the pet, and the pet. The owner is pleased by a pet food which has an appearance close to that of meat. The pet is pleased by a pet food which has an acceptable taste, odor, and other features. Inherent in a meatlike appearance, is a red coloration. One means of achieving a red coloration in a pet food containing meat, or blood is the use of a salt such as sodium nitrite. When present in an aqueous environment, the nitrate ion is in equilibrium with nitrous acid and nitric oxide. The nitric oxide potentially reacts with either the meat protein, myoglobin, or the blood protein, hemoglobin. The specific locus of the combination between such proteins and nitric oxide is believed to be the iron molecule which is permanently present as a reactive site normally reserved for the binding of oxygen. The above proteins carry out the physiological purpose of oxygen transfer to the body. When the binding between the nitric oxide and the protein occurs in combination with heat sufficient to denature or precipitate the protein, a heat-stable, acetone-extractable, red pigment is established. This pigment accounts for the acceptable color in many pet foods. The basic problem with the use of the nitrite to achieve the desired color is the fact that it has undesirable characteristics when consumed. It may be a carcinogen or react to form a carcinogen. These undesirable characteristics render it necessary to find a replacement for the nitrite ion which will achieve the desired color results without having an adverse effect on the pet food.
Further complicating the coloration for foods is the recent banning of dyes which have a long history of use in foods as colorants. This ban, imposed by governmental regulations, further limits the ability of food processors to achieve suitable coloration in the product. A great benefit to the industry may accrue if the coloration problem for the foods can be solved in an acceptable fashion.
Another basic problem with color-stabilizing the above-referenced meat proteins is that the complex formed is more stable when the iron in the protein is in the (Fe II) state. However, it is difficult to maintain that state. The (Fe III) state is more stable. Therefore, the iron content tends to oxidize to the (Fe III) state before the stabilization effect takes place. It is, therefore, desirable to stabilize the above-referenced proteins while maintaining the iron content thereof in the (Fe II) state.
Color is also important for a semi-moist pet food. Semi-moist pet food provides a meat-like appearance to which color greatly contributes and has a moisture content generally ranging from about 15 percent to about 50 percent. Since semi-moist pet foods are higher in moisture content than dry and lower in moisture than canned, special techniques are required to render it microbiologically stable. This moisture content in combination with special techniques may produce a microbiologically stable food which does not require refrigeration. At the same time, the higher moisture content of the semi-moist pet food provides an increased palatability when compared to the dry pet food. The semi-moist pet food is generally rendered microbiologically stable by using high levels of sugar and solutes, or other suitable means. In this fashion, shelf stability without refrigeration is achieved while providing a food having increased palatability relative to dry pet food. If a stable color can be provided for these semi-moist foods, color may be added to the listed advantages thereof.
The stabilization of color in food products is a problem in the art -- especially in semi-moist pet foods -- in view of the recent government bans on food dyes. Yet the final product appearance aspect renders color stabilization important to semi-moist pet foods.